Problem in my Lagrange's Equation program

[rpfant]

Dear all,

I am doing "Exercise 1.19. A two-bar linkage".

When I used scheme to find the Lagrange's equations, I got the
following result:

(down (??? x) (??? x))

Does it mean that the result is too big and cannot be display?

Or there are bugs in my code?

Best Regards,
rpfant

[rpfant]

My source code may help:

(define ((T-twobar m1 m2 m3 l1 l2 g x1 y1) local)
(let ((t (time local))
(q (coordinate local))
(qdot (velocity local))
)
(let ((vx1 (D x1))
(vy1 (D y1))
(theta1 (ref q 0)) (theta2 (ref q 1))
(thetadot1 (ref qdot 0)) (thetadot2 (ref qdot 1))
)
(+ (* 1/2 m1 (square vx1)) (* 1/2 m1 (square vy1))
(* 1/2 m2 (square (- vx1 (* l1 thetadot1 (sin theta1)))))
(* 1/2 m2 (square (+ vy1 (* l1 thetadot1 (cos theta1)))))
(* 1/2 m3 (square (- vx1 (* l1 thetadot1 (sin theta1))
(* l2 thetadot2 (sin theta1)))))
(* 1/2 m3 (square (+ vy1 (* l1 thetadot1 (cos theta1))
(* l2 thetadot2 (cos theta2))))
))
)))

(define ((V-twobar m1 m2 m3 l1 l2 g x1 y1) local)
(let ((t (time local))
(theta (coordinate local)))
(let ((theta1 (ref q 0)) (theta2 (ref q 1))
)
(+ (* m1 g y1)
(* m2 g (+ y1 (* l1 (sin theta1))))
(* m3 g (+ y1 (* l1 (sin theta1))
(* l2 (sin theta2))))
))
))

(define L-twobar (- T-twobar V-twobar))

(show-expression
(((Lagrange-equations
(L-twobar 'm_1 'm_2 'm_3 'l_1 'l_2 'g (literal-function 'x_1)
(literal-function 'y_1)))
(up (literal-function 'theta_1) (literal-function 'theta_2) ) )
't))